When persons discuss with each other on a conference, a sound recorder or an audio conferencing apparatus is mostly placed at a center of conference participants (a center of conference desks, and the like). For example, Patent Literature 1 proposes an audio conferencing apparatus which collects sound of the conference participants existing around the apparatus. In the apparatus as set forth in Patent Literature 1, a recessed part is formed on an upper surface of a disk-shaped housing, and a plurality of microphones are arranged on a bottom surface of the recessed part as viewed from an upper side of the housing. The microphones are arranged on a circle as viewed from the upper side of the housing. Each of the microphones has a unidirectivity and is disposed so that the directivity of the microphone is directed toward a center direction as viewed from the upper side of the housing.